A method for depositing a coating comprising a polymer and impermeable dispersed solid on a substrate, comprising the following steps: discharging at least one impermeable dispersed solid in dry powder form through a first orifice; discharging at least one polymer in dry powder form through a second orifice; depositing the polymer and/or impermeable dispersed solid particles onto said substrate, wherein an electrical potential is maintained between the substrate and the impermeable dispersed solid and/or polymer particles, thereby forming said coating; and sintering said coating under conditions that do not disrupt the activity and/or function of the substrate. A similar method is provided for depositing a coating comprising a hydrophobic polymer and a water-vapor-trapping material on a substrate.